Electric switch



Nov. 6, 1 928.

C. D. AINSWORTH ELECTRIC SWITCH 3 Sheets-Sheet 1 Filed Sept. 21, 192'! jrlverl?o?i c. D. IAINSWORTH ELECTRIC SWITCH Filed 11. 21, 192'! s Sheets-Sheet 2 Patented Nov. 6,1928.

umrao STA? I v 1,690,995 PATENT OFFICE. 4

damn i). amswonrmor worms'roiv, massacnoss'rrs, ASSIGNOR 'ro coNnrr ELECTRICAL MANUFACTURING CORPORATION, OF SOUTH BOSTON, MASSACHU- sa'r'rs, ACOBPORATION or msjsaonusnrrs.

ELECTRIC SWITCH.

Lpp11dation1flle6 September 21, 1927. Serial No 221,071.

I This invention-relates to enclosed electric switches especially adapted to carry heavy alternating currents. Y p

' The electric switch with which thisjinvention is particularly concernedflcomprisesan oil receptacle and a switch frame which comprises a cover for the oil receptacle. Massive insulated studs are carried by the switch frame and are immersedin the oil in the receptacle and one or morebridging members constituting the movable switch member are disposed in the oil and are movable into and out of engagement with. the studs.

The oil receptacle is composedof, sheet iron, asboiler plate and is strong'to resistthe high internal pressures that may be developed upon circuit interruption under heavy load. Under some conditions of operat on, as when the switch iscalled upon .tocarry an exceptionall heavycurrenuit isfound that r the side wa ls of the oil receptacle become hot and heatis transmitted through the oil 1 to the other parts of the. switch andso raises the tem' rature of the entire switch and'thus limits t e eurrenthcarrying ability of the switch. The heat is developed in the side walls of the oil receptacle byhysteresis and eddy currents set; up thereln; since the; arrangement of the conducting "studs/and bridging-member is: such as to iorma U which isipractically the equivalent. of a one turn solenoid and thus sets up a magnetic flux which acts upon the side walls of the oil receptacle. The side walls are'made of2 3 v sheet iron of a character, as boiler plate, I which is not a'particularlyi good imagn tlc conductor since it has, lug

of the side walls. a

It is an objector this invention. to reduce the heating of an electric switchof the above.

type by providing the sidewalls ofthe enclosing casing, or of the. oil-receptacle,w1th a c from the action of the 'alternatingmagnetic.

flux in the vicinity of; the current cenducting components of the switch.

provision of a magnetic shieldfor the] wall hysteresis, 1 and teddy currentlosses thereinand theseinternal losses are largely responsible. for the heatlng by beingcomposed of material having lower magnetic losses than the material of which the sidewall is composed, thus toreduce the heating of the casing. a

A further object of the invention is generally to lmprovetheconstruction and operation of electric switches and equivalent apparatus.

Fig- 1 isa sideelevation illustrating two of the; three switches of a three phase switching apparatus especially adapted for the control of circuits traversed by heavy currents.

Fig; 2 is a sectional elevation taken. along line 2-2 of Fig. 1. i

Fig. 3 is a sectional elevation taken along line 33 of Fig. 2. j

Fig. 4 is a perspective; view of oneof the oil receptacles of the switch, partially broken away to illustrate the magnetic shield forming a feature of this invention.

Fig. .5 is a perspective viewof one of the magnetic shields; W I g c The switch here shown asembodying the invention comprises an oil receptacle, 10 of rectangular shape and a, cover 12 which is suspended from the box-like casing 14 in which the switch operating mechanism is contained, V V

The oil receptacle is secured removablyto the coverplate or switch frame by bol'tsand wingnuts 16. The stationary switch members 18 and '20, formingv the opposite poles of the switch,;comprise a seriesof horizontally spaced vertical bars 22 which are connected electrically together and are passed through switch member comprises two sets of bars 22.

The movable switch member comprises a plurality ofmassive brush members 28 each of whichis carried at thelower endof an inasboiler plate and has relatively thick side A further object of the invention -1s the walls 34. 1 Said side walls arerelatively; closely spaced to the conducting components ofthe switch and are thus in the magnetic-field. sur

rounding said components and thus the side walls become heated by reason of the hysteresis and eddy current losses therein.

In accordance with this invention, I provide a magnetic shield which is interposed between the side walls of the receptacle and the conducting components of the switch for the purpose of shielding said side walls from the magnetic flux of the current carrying components, thus to prevent the generation of heat in the side walls.

The specific magnetic shield herein illus' trated comprises two U-shaped members having'the legs 36 and 3S- and the integral connecting member e0; Said shields are composed of a plurality of laminations of U-shape assembled to form a shield of substantial thickness. The laminations are composed of electrical steel which is characterized by having high permeability and low hysteresis and eddy current losses as compared with the steel of which the oil receptacle is constructed. Said shields are disposed in the opposite ends of the oil receptacle to lie against the inner face of the Side wall thereof and the ends of the shield are for convenience in manufacture terminated adjacent each other or are provided with a small vertical space or gap between the oppcsed legs thereof. The usual insulating lining 42 is disposed within the oil receptacle and against said shields. Said shieldsare against the side walls of the oil receptacle from a point at the top of the side walls and are extended downwardly at least throughout the zone of the magnetic field surrounding the current .conducting components of the switch and preferably are extended down to and rest upon the bottom wall of the oil receptacle whereby to be selt-supporting, with the insulating lining 4:2'l1 Olding said shields in place against the side walls of the tank. As thus arranged, the magnetic flux surrounding the conducting components of the switch that'ordinarilywould pass into the side walls of the-oil receptacle is caused to pass through the magnetic shield and is mainly excluded from t-he'oil receptacle. Since the material of the shield has a high permeability and very much lower hysteresis and eddy current losses than the material of the oil receptacle, it is apparent that the generation of heat in the oil receptacle by the alternating magnetic flux'will largely be prevented and since the iron losses in the shield are much lower than those in the tank, the losses in'the shield will not be high enough to set up any appreciable heating in the shield.

I claim:

1. An electrical apparatus having at current conducting component and a member normally disposed in the magnetic field of said component and liable to be heated by the alternating magnetic flux surrounding said component, and means interposed between said member and said current carrying component characterized by shielding said member against the magnetic flux surrounding said current conducting component, said shielding means being further charactertized by having hysteresis and eddy current losses which are materially less than the cone sponding losses of said member.

2. An electrical apparatus having an enclosing casing and a currentconducting component disposed within said casing and having an alternating magnetic field surrounding it which acts on said casing, and a mag netic shield interposed between saidcurrent conducting component and said casing in position to isolate said casing from the influence of said'magnetic field. e

3. An electric switch having anenclosing casing, switch terminals extended into said casing, a movable bridging member disposed within said casing in cooperative relation with said terminals, and a magnetic shield interposed between said terminals and the wall of said enclosing casin 4. An electric switch comprising an enclosing casing having a side wall of magnetic material, stationary and movable switch members disposed within said casing, and a. magnetic shield interposed between said switch members and said wall of said casing.

5. An electric switch comprising an enclosing casing having an iron side wall, stationary and movable switch members dis osed within said casing, and a magnetic shie d interposed between said switch members and said wall of said casing, said magnetic shield characterized by having materially lower hysteresis and eddy current "losses therein than the said losses of said iron wall.

' 6. An electric switch having an enclosing casing liable to become heated by the alter 105 nating flux surrounding the current carrying components of the switch, and means to shield said casingfrom said magnetic flux.

7. An electric switch having an enclosing casing liable to become heated by the alternating flux surrounding the current carrying components of the switch, and means to shield said casing from said magnetic flux, said shielding means being interposed between the current'conducting components of 11 the switch and said casing and characterized by having lower magnetic losses therein than the losses in said casing.

8. An electric switch having an enclosing casing, stationary and movable switch members disposed in said casing, and a pair of magnetic shields disposed within said casing adjacent the wall thereof and having their ends disposed in proximate relation.

9. An'electric switch having an oil conof magnetic field surrounding said switch members within said casing.

10. An electric switch comprising an enclosing casing having a rectangular oil containing receptacle, stationary and movable switch members immersed in the oil in said receptacle, anda pair of U-shapedmagnetic shields disposed within said casing atand overlying the inner face of the side walls thereof and interposed between said side wall and said switch members and having proximate ends. 1 p v 11; An electric switch comprising an enclosingcasing having a rectangular oil containing receptacle, stationary and movable switch members immersed in the oil in said receptacle, a pair of U-shaped magnetic shields disposed within said casing'at and overlying the inner face of the side walls 20 thereof and interposed between said side wall and said switch members and having proxi mate ends, and an insulating lining disposed within said oil receptacle and said magnetic shields.

12. An electric switch having an enclosing casing provided with a side Wall of magnetic material, stationary and movable switch members disposed within said casing, and a magnetic shield disposed within said casing and interposed between said switch members and the sidewall. of said casing, said magnetic shield composedof a plurality of laminations of magnetic material characterized by having higher permeability and lower magnetic losses than the material of said sidewall.

In testimony whereof, I have signed my name to this specification.

CHESTER I D. AINSWORTH. 

